Formaldehyde dehydrogenase (FDH) or glutathione-dependent formaldehyde dehydrogenase (FDH or xx-alcohol dehydrogenase) constitutes one of the two pathways by which living organisms detoxify formaldehyde. It specifically oxidizes s-hydroxymethyl-glutathione (an adduct formed between glutathione and formaldehyde) to s- formylglutathione with concomitant reduction of NAD+. FDH also oxidizes long-chain primary alcohols. This proposal aims at studying the catalytic mechanism of formaldehyde dehydrogenase by structural and kinetic methods. Structural studies involving X-ray crystallography will specifically aim at studying the structural changes in the enzyme during substrate binding and catalysis. Kinetic studies involving isotope effects and presteady state kinetics would aim at determining the entire kinetic mechanism of FDH including the rate of structural changes observe by crystallography. The structural and kinetic approach will complement each other in rigorously analyzing the events occurring during catalysis by this enzyme. Knowledge of the catalytic mechanism of FDH will lead to an understanding of the process that contributes significantly to the detoxification of formaldehyde.